Fracture toughness and cohesive fracturing properties of two classes of sandy-clay soils, (A) with fine and (B) coarse grains and stabilized with low (2%) and high (10%) cement (as soil stabilizer), were investigated using a chevron-notched semicircular bend (CN-SCB) sample under static and cyclic loads. The samples with coarser grains and higher amounts of cement stabilizer showed higher KIc compared to the soils containing low cement and fine grains. A noticeable reduction in KIc was also observed under cyclic loading compared to the monotonic loading. Load-crack opening displacement (COD) graphs obtained during cyclic loading showed high plastic deformation accumulation before the final fracture. The cycles required for the fatigue crack growth of the Class A soil were noticeably (three to six times) higher than the Class B. The FRANC2D nonlinear simulations, cohesive fracture analyses, and maximum stress theory were utilized for estimating the critical crack length and the onset of cohesive unstable crack propagation.

Cement stabilization of soils is a common technique to enhance engineering and mechanical properties of in situ soils in the field of road geotechnics. Usually, moderate quantities of cement are used, around 5-10% of the dry material. However, cement manufacturing is one of the biggest sources of greenhouse gas emissions, specifically carbon dioxide. For this reason, reducing cement content by a few percent in geotechnical structures made with cement-stabilized soils (CSS) has a high environmental interest, particularly in view of the involved volumes of material. This work aims to contribute to a better understanding of the mechanical characteristics of lightly stabilized soils. First, the mechanical behavior of a clayey and a sandy soil treated with 3% cement was studied for several curing times. Next, measured mechanical features were correlated. Finally, these measurements were used to characterize the Mohr-Coulomb failure criterion and compared with a conventional approach. Results point out that mechanical enhancement can be quantified in terms of cohesion. Friction angle seems to be independent of curing time. The proposed approach can be adapted in geotechnical applications based on the Mohr-Coulomb yielding criterion such as stability slopes, foundations, and retaining structures.

The present study has focused on stabilizing the soils of the embankments and improving the mechanical properties of gravel in subbases of pavements with different contents of bottom ash from thermal power plants and low percentages of lime. The density, humidity, simple resistance strength and bearing capacity of the new materials resulting from this combination have been studied. The results indicated that the optimal proportion of bottom ash added to the analyzed soil is 15%, while the optimal addition of lime is 1% for application in embankments and 2% for application in road subgrades. In clay soil that has a low simple resistance strength when 25% of bottom ash is added without lime, it can double the resistance. In the case of the gravel evaluated, it was found that the optimal ratio between the addition of bottom ash and lime is 6.5. In conclusion, it can be noted that soil that does not have any resistance when certain percentages of bottom ash are added, its properties are improved to be used in embankments.

The importance of physical, chemical, and mineralogical properties in selecting soils stabilized by activated natural pozzolan (ANP) was demonstrated. Five soil banks were identified, and two were selected: B1Z due to its SiO2 content and the presence of Montmorillonite and B3M for its granulometry and plasticity. Electrical con- ductivity (EC) was measured to monitor reactivity by testing two stabilizers, ANP and lime. Soils with 2.5% ANP exhibited higher EC than those with 10% lime. Compressive strength (CS) was analyzed. Soils with 10% ANP recorded higher CS than those with lime. Chemical and mineralogical properties were more relevant than physical ones in selecting soils stabilized through ANP.